Method of spraying concrete

ABSTRACT

A method of producing concrete includes admixing with dry cement the amount of water for producing complete setting, thoroughly beating the cement and water, and adding substantially dry sand or aggregate. The water-cement mixture is usually too stiff to be workable, but is reduced by the beating action to a less viscous product, capable when aggregate is added thereto of being blown into a reinforcing material such as a wire screen and of penetrating through the screen into contact with a backing. The amount of water is preferably of the order 35 - 37 lbs. per 100 lbs. of cement. The equipment for carrying out the spraying may be such that compressed air alone is used to provide the power for stirring and to transport the material.

United States Patent Cornwell et al.

- [451 June 13, 1972 METHOD OF SPRAYING CONCRETE [72] Inventors: CharlesE. Cornwell; James H. Backus, both of Alexandria, Va.

[73] Assignee: Jennings Bailey, Jr., Frederick, Md. [22] Filed: July 14,1969 [2 1] Appl. No.: 841,298

2,758,945 8/l956 Widmayer ..259/l47X 3,026,094 3/1962 True ..259/147Primary E.\'aminerRobert W. Jenkins Attorney.lennings Bailey, Jr.

[ ABSTRACT A method of producing concrete includes admixing with drycement the amount of water for producing complete setting. thoroughlybeating the cement and water, and adding substantially dry sand oraggregate. .The water-cement mixture is usually too stifi' to beworkable, but is reduced by the beating action to a less viscousproduct, capable when aggregate is added thereto of being blown into areinforcing material such as a wire screen and of penetrating throughthe screen into contact with a backing. The amount of water ispreferably of the order 35 37 lbs. per 100 lbs. of cement. The equipmentfor carrying out the spraying may be such that compressed air alone isused to provide the power for stirring and to transport the material.

4 Claims, 8 Drawing Figures PATENTEDJUN 13 I972 SHEET 10F 4 INVENTORS mn i W? m a J M M w: P u

PATEN'IEB UN 13 m2 SHEET 2 0F 4 INVENTORS J0 ATTORNEY M Z 5 5 M 2 M Q MZ Y sum 3 or 4 PATENTEDJUN 13 I972 I INVENTORS O/flPMZS E. (ORA/WELL,JFMES M 5 I ATTORNEY BACKGROUND OF THE INVENTION 1. Field of theInvention The invention relates to a method of producing concrete, aswell as to a method of spraying concrete so produced and a nozzle foruse in the spraying process.

2. The Prior Art It has been known in the past to spray a slurry ofconcrete containing water, cement and sand or aggregate. Such procedureshave not been particularly satisfactory because of the difficultiesinvolved in obtaining proper uniform consistency capable of beingprojected through a spray nozzle. Most cements when admixed with waterat the rate of 35 37 lbs. of water per 100 lbs. of cement produce asubstantially unworkable mixture, incapable of being sprayed orotherwise worked to a desired final form. The addition of more water tomake the product workable results in a decrease in the final strengthafter the cement is set.

When water, cement and aggregate such as sand are admixed in quantitiesnecessary to produce a workable product, because of the absorption ofsome of the water by the sand, extra water is required in order toprovide the amount necessary for reaction with the cement duringsetting. This extra water results in reduced strength in the final setproduct.

It has been found that the use of a flurry of the type according to theinvention causes totally impermissible wear on ordinary pumps, becauseof the abrasive nature of the slurry.

' SUMMARY OF THE INVENTION of a Applicants have found that it ispossible to produce a concrete which when set has substantially greaterstrength than normal concrete, without the requirement of expensiveadditives, by mixing together cement and just enough water to set thecement, this being in most cases an amount of the order of 3537 lbs. ofwater per 100 lbs. of cement, and then subjecting the normallyunworkable mixture to violent beating in a blender, which results inproducing a much less viscous and more workable slurry of water andcement. This slurry is then admixed with dry sand, preferably by blowingthe slurry and the sand at moderate pressures and speeds through anozzle, upon a surface which may have reinforcing material thereon suchas wire mesh or expanded metal. It has been found that the resultingconcrete will penetrate the mesh of the wire and will when set havesubstantially greater strength than normal concrete, even of the typewhich is not sprayed.

It is also contemplated that, for purposes of placing concrete inmoulds, the cement and water will be first thoroughly admixed and thencharged into an ordinary concrete mixer with dry sand and mixedtherewith while being transported to the job.

A further important feature of the invention is the provision of anapparatus for forming the mixture of slurry and sand, and spraying it ona surface to be coated, which is operable entirely by air pressure andwhich does not rely on ordinary pumps for propelling the sand andslurry. This apparatus is extremely simple in construction, but iseffective in producing the mixture of sand in the slurry and spraying iton the surface to be coated by means of air pressure alone, avoiding theabrasive action on pumps which makes the life of other spraying devicesimpractically short.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 shows in side elevation, partly in section, a wall or other rigidproduct produced according to the invention;

FIG. 2 shows an arrangement for mixing and pumping the cement and water;

FIGS. 3 and 4 show two forms of spray nozzles;

FIG. 5 shows a modified form of apparatus for carrying out theinvention;

FIG. 6 shows a detail of FIG. 5;

FIG. 7 is an end view ofFlG. 4;

F 10. 8 shows another form of apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows in cross-section apart of a structure in the production of which the present invention isused. This may be for example the hull of a boat. It includes ribs suchas 2 for a bulk head and attachments, to which is attached a sheet 4 ofplywood, plaster board or the like. To this sheet are attached secondribs 6, between which are plates 8 of foamed styrene or the like. Tothese ribs are secured by staples 10 a number of layers 12 of wire mesh,for example ordinary l-inch chicken wire, or expanded metal or both,Above these are secured wire rods 14, and on top of these further layers16 of wire mesh. According to a particular feature of the invention, acement slurry is sprayed on this reinforcement structure. A particularfeature of the invention is that the slurry is such that it canpenetrate through the wire and the expanded metal and adheretightly toit and the foamed inserts, while at the same time its strength is verysubstantially greater than that of a normally sprayed concrete slurry.The chicken wire used is ungalvanized for better adhesion.

According to the invention a mixture of cement and water, preferably inthe proportion of 35 37 lbs. of water to lbs. of cement, is introducedinto a drum such as that shown in FIG. 2 at 18. This drum containsheaters 20 driven by a motor 22 which stir the water and cement. Themixture leaves the tank through a pipe 24, being drawn by a pump 26which feeds it through a pipe 28 to the spray gun described below. Arecirculating pipe 30 contains a check valve 32 which is fed so as toopen at a pre-determined pressure, for example 50 PSI, so that thepressure of the material in the pipe 28 is controlled at this value.

The pipe 28 is connected to a nozzle which may bc'of the type shown inFIG. 3. This nozzle includes a spray tip 36 connected to a pipe 38 withwhich the pipe 28 is connected, with a valve 40 by which it may beclosed.

The proper amount of sand, for example to 200 lbs. per each 100 lbs.-ofcement, is fed from a conventional type of sand tank from which it isremoved by compressed air at a pressure of substantially the samepressure as that which exists in pipe 28 and is fed to pipe 42 connectedto pipe 38 through manually operated valve 44.

Such a nozzle will put out about 12 lbs. per minute of watercementslurry, with 14 lbs. of sand per minute (volume weight). 1

The slurry formed in the tank 18 is very difiicult to handle, because ofits high viscosity, but, if it is sufficiently agitated and stirred bythe pump 26, its viscosity will be substantially reduced. In fact, theviscosity is sufiiciently reduced so that it can be pumped through thespray gun and will penetrate a number of layers of wire or expandedmetal. The sand, being added only just before it is sprayed from thegun, does not need to be wet, and therefore does not require additionalwater which would reduce the strength of the set concrete and impair itssetting properties. On the other'hand, the sprayed concrete according tothe invention does not set appreciably faster than a normally sprayedconcrete mix.

The material may be sprayed not only on a level surface but also on avertical or downwardly sloping surface. The procedure requirescomparatively little air, of the order of 40-100 cubic feet per minutefor 26 lbs. of the concrete mix.

The resulting concrete when set is substantially stronger than normalconcrete mixes, and is free of bubbles and other flaws.

FIG. 4 shows another form of nozzle. In this the pipes 28 and 42 meetopposite each other opening into the nozzle 46 at right angles to itslongitudinal axis. The nozzle 46 encloses a shaft 48 carrying vanes 50.An additional air current is introduced through pipe 52, which throughan air motor 54 drives the shaft 48. The shaft 48 is hollow, and itsinterior is connected to the air pipe 52 beyond the air motor 54. Thepipe extends slightly beyond the free end of the noule, as at 56, andhas lateral openings 58 through which the air escapes. The air jets thusproduced tend to spread out the mixture of sand and water cement beingexpelled from the nozzle so as to distribute it more evenly over thearea sprayed. The vanes 50 and the inner lining of the nozzle arepreferably of rubber.

FIGS. -6 show a spraying apparatus which is operated by air pressurealone, so that it can be worked by an air compresser mounted on a truckor other carrying vehicle, without the need for any electrical motor.

In this form of the invention, tank or blender 62 is used for containingcement and water and tank 64 for sand. These tanks are covered by lids66 which may be hinged at 68 and provided with sealing clamps 70 to holdthem tight. In the lid of each tank is a manually operable valve 72, 73.

The air compresser 74 supplies air under pressure through a T-connection76 to pipes 78 and 80. Pipe 80 is connected to an air motor 82 at thebottom of tank 62, which drives a bladed agitating shaft 84 within thetank. This air motor may be a simple shaft with extending curved vaneswhich are impinged by the air from the pipe 80 entering tangentiallyinto the motor 82. The outlet of the motor casing 82 is connected by apipe 86 to the interior of the lid 66 of the tank 62. In the bottom ofthe tank 62 is an outlet connected to a pipe 88, which in turn leadsinto an interchangeable washer-holding control member 90 and to a spraygun 92. This gun may be for instance either of the type shown in FIGS. 3and 4.

The There 78 leads to the top 66 of tank 64. There is also a connectingpipe 94 leading from the interior of the lid 66 of tank 64 to aT-arrangement 96 as shown in more detail in FIG. 6. The other branch ofthis T connects with a pipe 98 which leads to the spray gun 92.

The T-arrangement shown in FIG. 6 includes a nipple 100 welded to thebottom of the tank 64 against the end of which rests a gasket 102 and ametal washer 104 having an opening 106 therethrough, the gasket andwasher being clamped by a shoulder 108 on the T 96 against the end ofthe nipple 100. This arrangement makes it easy to interchange the washer104 to adjust the flow of sand. In a device here shown, and operatingwith a pressure of 50 PSI, an opening of /4 inch has been found to giveproper flow of sand.

In the use of this device, the valves 72 and 110 are opened while valve112 is closed. The compresser then supplies compressed air through pipe80 to air motor 82, and by rotating the shaft 84 and agitating thecement-water mixture of the proper proportions forms a slurry. Ifhowever, it is desired to use the device more frequently without waitingto produce the slurry in the tank 62, the slurry can be made up intoanother tank and simply dumped into the tank 62. Assuming the tank isfilled with slurry of a gel-like consistency of the type whichcharacterizes the invention, the valve 72 is closed (valve 73 alreadybeing closed) and valve 112 is opened. The result is that pressurebuilds up in the covers 66 of the tanks. Pressure in the tank 62 forcesthe cement-water slurry into the pipe 88 and through the orifice 90 tothe spray gun 92. Because the air enters tank 66 only slowly, when ithas once built up pressure therein, to replace the slurry which is beingsprayed from the tank, the air motor will be rotated only slowly, butenough to maintain the slurry in its proper condition. At the same time,the pressure in the top of tank 64 will be exerted on the top of thesand and will force it down through the T 96 into the line 98. At thesame time, the air will pass through line 94 to the T 96 and will therepick up the sand and convey it through the line 98 to the spray gun 92.This continues until the tanks are empty, where upon they are rechargedand the procedure described above is repeated.

Of course the pressure provided by compresser 74 is sufficiently greatas compared with the size of pipe 94 so as to build up a substantialpressure in the lid 66 of tank 64 and thereby to produce the dischargeof the sand from the bottom of the tank.

The rate of sand discharge can be adjusted by varying the pressure ofthe compresser, or by interchanging the washers at and 104.

The tanks in the apparatus shown have a capacity of approximately 50gallons each. Using air at 50 lbs. pressure, they will sprayapproximately 25 lbs. of cement-water and sand mix per minute, thusoperating for approximately 50 minutes before refilling if necessary.

While we have described the use of sand as an additive, other solidparticulate aggregate material such as gravel may be used.

The device shown in FIG. 8 includes a tank with a removable top forreceiving dry cement. Mounted by a spider 122 within the tank is a motor124 which drives an auger 126 for feeding the material through the wallopening 128. From there it passes through a volume control device 30which is connected to the motor to cause the motor to operate at such aspeed as to deliver a predetermined amount of cement per unit of time.The cement then passes through a blender 132 which also receives waterthrough a pipe 134. The outlet pipe 136 of the blender is adapted todeliver the blended mixture to a tank truck 138.

The blender may be of the type known as a shear-flow blender, withrecirculation, of the type produced by Tensco, of Barrington, R. I.,having a number of turbine-like blades.

In the use of this apparatus, the cement and water are blended in theblender, thus being beaten to a condition of lower viscosity and are fedinto the tank truck. The truck is then moved to another position-fromwhich it receives dry sand or aggregate, which is then mixed by therotation of the tank with the slurry previously formed.

What is claimed is:

1. In the placing of concrete, the steps of admixing cement with waterin a quantity just substantially great enough to produce setting of thecement, thereby forming a relatively viscous material, beating saidmaterial vigorously until its viscosity is substantially reduced to forma slurry, and admixing substantially dry aggregate material with saidslurry.

2. A process as claimed in claim 1, in which the proportion of water tocement is substantially 35-37 lbs. of water per I00 lbs. of cement.

3. A process as claimed in claim 1, in which said aggregate material andreduced-viscosity slurry are fed through a mixing nozzle, at least theaggregate material being propelled into and through said mixing nozzleby a carrying current of air under pressure.

4. A process as claimed in claim 3, in which the aggregatematerial-cement mixture from said nozzle is sprayed onto a backingsurface with meshed reinforcing material secured with meshed reinforcingmaterial secured on the face thereof on which the mixture is sprayed.

2. A process as claimed in claim 1, in which the proportion of water tocement is substantially 35-37 lbs. of water per 100 lbs. of cement.
 3. Aprocess as claimed in claim 1, in which said aggregate material andreduced-viscosity slurry are fed through a mixing nozzle, at least theaggregate material being propelled into and through said mixing nozzleby a carrying current of air under pressure.
 4. A process as claimed inclaim 3, in which the aggregate material-cement mixture from said nozzleis sprayed onto a backing surface with meshed reinforcing materialsecured with meshed reinforcing material secured on the face thereof onwhich the mixture is sprayed.